Lofland, John, author
Wadsworth, 1971
Buku Teks
Lofland, John, author
Wadsworth, 1984
Buku Teks
Strauss, Anselm L., author
Cambrigde University Press, 1987
Buku Teks
edited by Alan Bryman, Robert G. Burgess
Routledge , 1995
Buku Teks
Andrews, Frank M.
University of Michigan, 1981
Buku Teks